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First Transnational User

Project 029

“Through the ASCENT network I quickly got access to the fabrication facilities and personnel. That helps me gain important data for my research project”

Liang Ye, University of Twente, Netherlands

SOI nanowires for nanowires ultra-shallow doping experiment
Access Type

This work involved the doping of silicon nanowires using monolayer contact doping (MLCD). MLCD is a modification of the monolayer doping (MLD) technique. It involves monolayer formation of a dopant-containing adsorbate on a separate source substrate that is subsequently brought into contact with the target substrate, upon which the dopant is driven into the target substrate by thermal annealing. The use of a source substrate provides a capping effect which prevents loss of dopants without having to use a capping layer on the target substrate which would require additional chemical removal. This allows easy application of this method on sensitive structures, including Si nanowires. We used here a boron-rich carborane adsorbate to construct the monolayer that delivers the dopant, to boost the doping level in the target substrate. The doping of silicon nanowires that were prepared by the ASCENT project were demonstrated and measurements performed by the ASCENT team proved incorporation of the dopant atoms into the silicon nanowires resulting in improved conductivity.

Monolayer doping (MLD) is an alternative doping technique with increasing interest in recent years. It offers the benefit of producing ultra-shallow doping without causing crystal damage. It is also suitable for doping 3D structures. Recently monolayer contact doping (MLCD) was proposed. MLCD eliminates the wet chemistry processing of the samples while retaining the benefits of MLD. In this work we want to demonstrate the tuning of electrical properties of silicon nanowires using ultra-shallow doping from MLCD. This opens up possibilities for refining nano-structuration and fine-tuning the properties.

ASCENT provided Si nanowires to investigate the electrical properties of the nanowires in relation to their dimensions (100-200 nm in width and height, few hundred nanometers to few microns in length) and the depth of the doping (10-20 nm range).

Work carried out via ASCENT
  1. Fabrication of nanowires on SOI substrate
  2. Electrical characterisation of undoped nanowires
  3. Electrical characterisation of nanowires following ultra-shallow doping at user facilities